1. Field of the Invention
The present invention relates to the field of hydrocarbon conversion and related processes and apparatus.
2. Description of the Prior Art
U.S. Pat. No. 3,479,093 teaches a feeder for fine particles utilizing pressurized feed tanks but which does not relate to fluid catalytic crackers, U.S. Pat. No. 3,437,384 teaches conveying systems for pneumatically conveying solid granular material, U.S. Pat. No. 3,253,866 also relates to pneumatic conveying of granular materials, U.S. Pat. No. 2,572,078 utilizes a rotatable tube communicating with a storage container and having a scoop which forces material into the inside of the tube, e.g., for dispersing iron powder in an oxygen-acetylene stream, and U.S. Pat. No. 2,524,919 entrains powder in a flowing stream of gases.
Various methods of feeding catalyst from storage tanks into airveyor systems have been utilized in the past, including primarily augers and star-wheel arrangements which have sometimes been susceptible to blowback when the wear or malfunction of the star-wheel permitted pressure from the pressurized conveying system to blow back into the low pressure catalyst storage tank.
None of the above prior art permits the invention's complete flexibility of addition while avoiding the use of any moving parts (other than the valves) which are in contact with the flowing catalyst. The present invention also avoids the need for load-cells and other weighing devices which require specialized maintenance procedures.